Protective Effect of Biomass Components Against Interfacial Inactivation of α-Pinene Oxide Lyase from Pseudomonas rhodesiae CIP 107491

Abstract

α-Pinene oxide lyase is able to catalyze the cleavage of both rings of α-pinene oxide to form cis-2-methyl-5-isopropylhexa-2,5-dienal (isonovalal) with no cofactor requirements. This bioconversion, when carried out under biphasic conditions (water/hexadecane) by Pseudomonas rhodesiae CIP 107491, allows the accumulation of a very high concentration of the product. Nevertheless, the reaction stopped due to the loss of enzyme activity, which has been demonstrated to be an irreversible phenomenon. The enzyme was purified by chromatographic methods to study the reasons of its instability. Bioconversion with pure enzyme showed that a protein precipitation occurred at the liquid-liquid interface, giving rise to a decrease in soluble protein and in residual enzymatic activity. The rate of decrease in soluble protein concentration was not related to the presence of the precursor, which indicated that the inactivation was interfacial, i.e. due to the direct contact of the enzyme with the hexadecane layer. This phenomenon was not present when crude enzymatic extract was used as a biocatalyst. Biomass components present in this extract thus had a protective effect against interfacial phenomena, demonstrating that α-pinene oxide lyase purification does not attract much practical interest for isonovalal production.

Keywords

• bioconversion
• isonovalal
• interfacial inactivation
• Pseudomonas rhodesiae CIP 107491
• protective effect